INTRODUCTION TOBONDING

CHEMICAL BONDING

CHEMICAL BOND

• ATTRACTIVE FORCE BETWEEN ATOMS OR IONS THAT BINDS THEM TOGETHER AS A UNIT

• BONDS FORM IN ORDER TO…

• DECREASE POTENTIAL ENERGY (PE)

• INCREASE STABILITY

BONDS ARE… FORCES THAT HOLD GROUPS OF ATOMS TOGETHER AND MAKE THEM FUNCTION AS A UNIT. TWO TYPES:

1)Ionic bonds – transfer of electrons (gained or lost; makes formula unit)

2)Covalent bonds – sharing of electrons. The resulting particle is called a “molecule”

TYPES OF BONDS

IONIC COVALENTBond Formation

Type of Structure

Solubility in Water

Electrical Conductivity

OtherProperties

e- are transferred from metal to nonmetal

high

yes (solution or liquid)

yes

e- are shared between two nonmetals

low

no

usually not

MeltingPoint

crystal lattice true molecules

Physical State solid liquid or gas

odorous

TYPES OF BONDS

“electron sea”

METALLICBond Formation

Type of Structure

Solubility in Water

Electrical Conductivity

OtherProperties

MeltingPoint

Physical State

e- are delocalized among metal atoms

very high

yes (any form)

no

malleable, ductile, lustrous

solid

VALENCE ELECTRONS ARE…?

THE s AND p ELECTRONS IN THE

OUTER ENERGY LEVEL OR THE HIGHEST OCCUPIED ENERGY LEVEL.

THE ELECTRONS RESPONSIBLE FOR THE CHEMICAL PROPERTIES OF ATOMS.

ELECTRON DOT DIAGRAMS ARE…

• A WAY OF SHOWING & KEEPING TRACK OF VALENCE ELECTRONS.

• HOW TO WRITE THEM?

• WRITE THE SYMBOL - IT REPRESENTS THE NUCLEUS AND INNER (CORE) ELECTRONS

• PUT ONE DOT FOR EACH VALENCE ELECTRON (8 MAXIMUM)

• THEY DON’T PAIR UP UNTIL THEY HAVE TO (HUND’S RULE)

X

The Electron Dot diagram for Nitrogen

Nitrogen has 5 valence electrons to show.

First we write the symbol.

NThen add 1 electron at a time to each side.Now they are forced to pair up.

We have now written the electron dot diagram for Nitrogen.

The Octet Rule In Chapter 6, we learned that noble gases are

unreactive in chemical reactions In 1916, Gilbert Lewis used this fact to explain

why atoms form certain kinds of ions and molecules

The Octet Rule: in forming compounds, atoms tend to achieve a noble gas configuration; 8 in the outer level is stable Each noble gas (except He, which has 2) has 8

electrons in the outer level

OCTET RULE• METALS LOSE ELECTRONS TO ATTAIN A NOBLE GAS CONFIGURATION. FORM CATIONS (POSITIVE)

• NONMETALS GAIN ELECTRONS TO ATTAIN NOBLE GAS CONFIGURATION. FORM ANIONS (NEGATIVE)

• AN ATOM IS ELECTRICALLY NEUTRAL BECAUSE THE PROTONS AND ELECTRONS ARE EQUAL, IONS FORM WHEN THEY LOSE OR GAIN ELECTRONS.

COMMON ION CHARGES

1+

2+ 3+ NA 3- 2- 1-

0

IONIC NOMENCLATURE

IONIC NOMENCLATURE

IONIC FORMULAS• WRITE EACH ION, CATION FIRST. DON’T SHOW

CHARGES IN THE FINAL FORMULA.• OVERALL CHARGE MUST EQUAL ZERO.

• IF CHARGES CANCEL, JUST WRITE SYMBOLS.• IF NOT, USE SUBSCRIPTS TO BALANCE

CHARGES.• USE PARENTHESES TO SHOW MORE THAN ONE

POLYATOMIC ION.• STOCK SYSTEM - ROMAN NUMERALS INDICATE THE

ION’S CHARGE.

IONIC NOMENCLATURE

IONIC NAMES

• WRITE THE NAMES OF BOTH IONS, CATION FIRST.

• CHANGE ENDING OF MONATOMIC IONS TO -IDE.

• POLYATOMIC IONS HAVE SPECIAL NAMES.

• STOCK SYSTEM - USE ROMAN NUMERALS TO SHOW THE ION’S CHARGE IF MORE THAN ONE IS POSSIBLE. OVERALL CHARGE MUST EQUAL ZERO.

IONIC NOMENCLATURE

• CONSIDER THE FOLLOWING:

• DOES IT CONTAIN A POLYATOMIC ION?

• -IDE, 2 ELEMENTS NO

• -ATE, -ITE, 3+ ELEMENTS YES

• DOES IT CONTAIN A ROMAN NUMERAL?

• CHECK THE TABLE FOR METALS NOT IN GROUPS 1 OR 2.

• NO PREFIXES!

potassium chloride

magnesium nitrate

copper(II) chloride

K+ Cl-

Mg2+ NO3-

Cu2+ Cl-

KCl

Mg(NO3)2

CuCl2

IONIC NOMENCLATURE

NaBr

Na2CO3

FeCl3

sodium bromide

sodium carbonate

iron(III) chloride

IONIC NOMENCLATURE

CHEMICAL BONDING

MOLECULAR COMPOUNDS

LEWIS STRUCTURES• OCTET RULE

• MOST ATOMS FORM BONDS IN ORDER TO OBTAIN 8 VALENCE E-

• FULL ENERGY LEVEL STABILITY ~ NOBLE GASES

Ne

+ -

+

LEWIS STRUCTURES• NONPOLAR COVALENT - NO CHARGES

• POLAR COVALENT - PARTIAL CHARGES

MOLECULAR NOMENCLATURE

• PREFIX SYSTEM (BINARY COMPOUNDS)

1. LESS E-NEG ATOM COMES FIRST.

2. ADD PREFIXES TO INDICATE # OF ATOMS. OMIT MONO- PREFIX ON FIRST ELEMENT.

3. CHANGE THE ENDING OF THE SECOND ELEMENT TO -IDE.

PREFIX

MONO-

DI-

TRI-

TETRA-

PENTA-

HEXA-

HEPTA-

OCTA-

NONA-

DECA-

NUMBER

1

2

3

4

5

6

7

8

9

10

MOLECULAR NOMENCLATURE

CCl4

N2O

SF6

carbon tetrachloride

dinitrogen monoxide

sulfur hexafluoride

MOLECULAR NOMENCLATURE

arsenic trichloride

dinitrogen pentoxide

tetraphosphorus decoxide

AsCl3

N2O5

P4O10

MOLECULAR NOMENCLATURE

N O F

Cl

Br

I

H

MOLECULAR NOMENCLATURE

• THE SEVEN DIATOMIC ELEMENTS

BR2 I2 N2 CL2 H2 O2 F2